1. Field of the Invention
Embodiments of the invention relate generally to methods for processing a substrate during semiconductor manufacturing. Specifically, embodiments of the invention relate to methods of treating a nucleation layer prior to a CVD deposition process.
2. Description of the Related Art
Reliably producing nanometer-sized features is one of the key technologies for the next generation of semiconductor devices. The shrinking dimensions of circuits and devices have placed additional demands on processing capabilities. The multilevel interconnects that lie at the heart of integrated circuit technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is very important to future success and to the continued effort to increase circuit density and quality of individual substrates.
Metallization of features formed on substrates includes CVD deposition of metals such as tungsten. Tungsten can be used for metal fill of source contacts, drain contacts, metal gate fill and gate contacts as well as applications in DRAM and flash memory. As feature dimensions shrink, it becomes increasingly difficult to fill features with cross-sectional dimensions of less than 20 nm while maintaining the filled regions void-free. Additionally, post-processing steps such as CMP of the tungsten layer and tungsten etchback (dry and wet) can open voids or even seams to create integration problems if tungsten fill is not near-perfect.
Re-entrant features, in which the upper part of the feature is smaller than the lower part, cannot be filled seam-free by current techniques, even with 100% conformal tungsten processing. Tungsten CVD fill has evolved to near 100% conformality over the last 20 years. However, current techniques fail to achieve more fill inside features than on the field with conventional ALD-tungsten nucleation followed by tungsten halide and H2 bulk CVD fill. The resulting seams are exposed to slurry during tungsten CMP, or tungsten etch chemistry during tungsten etchback. The CMP slurry or etchback chemistry enters seams from tungsten CVD processing, enlarges them, and can lead to significant integration issues down-stream.
Therefore, there is much effort in the art to create a tungsten deposition process with enhanced bottom-up tungsten growth for seam-free tungsten fill of features.